Method of making a die-stamped circuit board assembly for photoflash devices

ABSTRACT

A circuit board assembly and method of making wherein the assembly includes a dielectric substrate, at least one radiation sensitive switch, and at least one conductive member in electrical contact with the switch. Portions of the switch and the conductive member are die-stamped into the dielectric substrate to achieve the contact without serving the switch material.

TECHNICAL FIELD

The invention relates to electrically-activated, disposable photoflashdevices and particularly to the circuit board assemblies utilizedtherein.

CROSS REFERENCE TO COPENDING APPLICATIONS

In Ser. No. 131,610, entitled "Photoflash Device Having Die-StampedCircuit Board Assembly With Flexure Means to Prevent Switch Cutting" (R.H. LeFever et al), there is described a circuit board assembly andphotoflash device utilizing same wherein the assembly includes flexuremeans within its dielectric substrate to enable pressing of theassembly's switch and conductor therein without severance of the switch.The flexure means comprises portions of reduced thickness within thesubstrate immediately below the switch ends, these portions flexingduring the described pressing operation. Ser. No. 131,610 is assigned tothe same assignee as the proposed, instant invention and was filed onMar. 19, 1980.

In Ser. No. 131,614, entitled "Die-stamped Circuit Board Assembly HavingRelief Means and Method of Making Same" (B. G. Brower et al), there isdescribed a circuit board assembly and a method of making same whereinthe switch and conductor are pressed into the assembly's dielectricsubstrate in such a manner that only preselected portions of the switchare either deformed or severed. These portions penetrate the substrate'supper surface at a depth greater than the remaining, non-deformedportions of the switch to provide enhanced securement. Ser. No. 131,614is assigned to the same assignee as this invention and was filed Mar.19, 1980.

BACKGROUND

Photoflash devices of the variety mentioned above typically include acircuit board having an insulative substrate with preestablished circuitpatterns or "runs" thereon. Electrically connected at designatedlocations to this circuitry are a plurality (e.g., eight or ten) of highvoltage flashlamps. The circuit board, with flashlamps secured thereto,is located within a suitable, insulative housing having alight-transmitting cover (to permit the high intensity output from eachflashlamp to pass therethrough) and at least one connector tab forattaching the device to a respective camera and electrically connectingthe circuit board's circuitry to the power source (e.g., piezoelectricelement) typically located therein. Activation of the power source bythe camera's user, such as by depressing the shutter release button,results in a firing pulse being provided the circuitry and ignition ofone of the device's flashlamps. One type of device containing a pair ofopposing linear arrays of flashlamps and a singular, common connectortab is referred to in the art as a "flash bar", while another type,which is capable of being inverted and thus possessing two opposingconnector tabs, is referred to as a "flip-flash". The " flip-flash"devices were designed primarily to substantially eliminate thephotographic phenomenon known as "red-eye", which occurs when light isreflected by the retinae of subjects' eyes onto the photographic film toindicate the eyes' pupils as being red. These latter devicessubstantially eliminate this possibility by spacing the illuminatingflashlamp a specified distance from the camera's lens.

One example of the aforementioned "flash bar" photoflash device isdescribed in U.S. Pat. No. 3,857,667 (J. J. Vetere et al). An example ofan eight flashlamp arrayed "flip flash" is described in U.S. Pat. No.4,113,424 (D. E. Armstrong et al), while examples of ten lamp versionsof this product are described in U.S. Pat. Nos. 4,152,751 (R. E.Sindlinger et al) and 4,164,007 (E. G. Audesse et al). All of the abovepatents are assigned to the assignee of the instant invention.

As stated, the present invention is concerned with the manufacture ofthe circuit board assembly which eventually forms an integral part ofthe final photoflash product. One example of a known technique formaking such components (e.g., those used in the aforedescribed "flashbar" device) has been to silk-screen a silver-containing material over aceramic-coated steel board and thereafter oven-fire the assembly to fusethe silver particles to a continuous conductor. The steel board wasoriginally blanked from a strip of said material, sprayed or dipped withthe ceramic, and fired to produce a hardened coating thereon.Silk-screening and oven-firing followed. Another type of technique(e.g., for those components used in many "flip-flash" devices) alsoinvolved silk-screening of silver-containing material but instead on astyrene copolymer, thermoplastic substrate (or board). Thesilver-containing material, applied in paste form, was then subjected toeither a radiation curing or hot air drying step. In both of the aboveexamples, the cured silver-containing material served as the conductivecircuit in the finished device. Yet another technique (as used in atleast one embodiment of a "flip-flash" device) involved approximatelythe same procedures as used to manufacture circuit board assemblies insuch products as television sets. This process required several steps,including photo-resist coating a copper-clad sheet of phenolic or othersuitable base material and thereafter chemically removing (e.g.,etching) the undesired copper. This component was then thoroughlycleaned and coated with a protective film.

The aforementioned techniques and resulting products contain severaldisadvantages. Silk-screening, for example, requires utilization ofpastes which in turn are comprised of discrete silver particles locatedtherein and separated by a binder. Although these pastes are eventuallysubject to some form of heat treatment to hopefully fuse said particles,the finished circuitry understandably is limited in its conductivity(and thus possesses an inherently higher resistance) in comparison toconductors presented in another state. Silk-screened circuitry is alsosusceptible to containment of discontinuities as might result from dustor lint interference during the screening operation. The presence of ascreened silver layer also poses a problem when the chosen method forsecuring the device's flashlamps to the circuitry is soldering.Occasionally, the silver layer has prevented proper wetting during thisprocess. Still another inherent problem with silk-screening conductivecircuitry is the ready opportunity for dimensional impreciseness due tothe horizontal flow (beneath the screen) as the paste is forced throughthe screen's pattern. In addition, occasional smearing of the circuitrun is practically unavoidable. The latter problems are particularlytroublesome to devices employing high voltage flashlamps in thatsparkover can then occur between the circuit's elements, resulting ineither product failure or simultaneous flashing of two or more lamps. Afinal disadvantage of the above processes is the relatively high costsassociated therewith. Techniques using photo-resist coating,development, and subsequent chemical removing are understandably costlyin terms of both time and material. Silk-screening is alsounderstandably costly, particularly as a result of using the preciousmetal silver and the relatively rapid wear of the screen materialstypically used in this process.

The present invention overcomes the several, aforementioneddisadvantages by employing the technique of die-stamping to thusaccurately define and position a conductive circuit on an insulativesubstrate without the need for photo-resists, chemical echtants,precious metals, etc. In addition to this, and of equal or greatersignificance, this technique as utilized in the present inventiondefines a procedure whereby the device's circuit runs (or paths) can besatisfactorily positioned and electrically connected to other elementswhich also constitute part of the device's circuitry without causingdamage thereto. One primary example of such an element as utilized intoday's more recent products is a radiation sensitive switch which isusually electrically connected in series with a respective flashlamp andadapted for receiving the radiant energy from the lamp upon ignitionthereof. The switch will thus melt or shrink to define an open circuitalmost instantaneously after flashlamp ignition and thereby permitreliable flashing of the subsequent lamps in the device's array in rapidsuccession. An example of a radiation sensitive switch is described inU.S. Pat. No. 4,017,728 (E. G. Audesse et al), which is also assigned tothe assignee of the present invention. As described therein, theseswitches each are typically comprised of a thin strip of polymericmaterial attached to the circuit board across a respective apertureprovided therein. A typical ten-lamp array will include eight switchesof this variety in view of the obvious understanding that the last firedlamp on each end of the array has no need for such an element. It isunderstood that the relatively delicate nature of such elements asradiation sensitive switches does not readily permit electricalconnection thereto by a technique as relatively severe and demanding asdie-stamping. Die-stamping has been utilized in the production ofprinted circuit components for use in other types of products than thosedescribed above but only because such components (and thereforeproducts) did not require elements such as radiation sensitive switchestherein. Typically, these products consisted of only a base orsubstrate, a solid metal conductor (e.g., copper foil), and a bondingadhesive. See, e.g., U.S. Pat. Nos. 3,911,716 (W. Weglin) and 3,990,142(W. Weglin). The invention as will be described is thus deemed all themore unique and significant in that it not only assures positiveelectrical connection between the component's circuit runs and delicateswitch elements but also provides for definition and securement of thecircuit runs to the insulative substrate which forms an integral part ofthe final product.

It is believed therefore that the aforedefined technique formanufacturing circuit board assemblies and the products resultingtherefrom will constitute significant advancements in the art.

DISCLOSURE OF THE INVENTION

It is therefore a primary object of the present invention to enhance theart of manufacturing circuit board assemblies for use in electricallyactivated photoflash products.

It is another object of the invention to provide a circuit boardassembly for use in said products.

In accordance with one aspect of the invention, there is provided amethod of making a circuit board assembly comprising the steps of: (1)positioning a dielectric substrate on a base; (2) locating at least oneswitching element on the substrate; (3) orienting a conductive stripover both substrate and element; (4) engaging the strip with a diemember to press portions of both the conductive strip and the switchingelement into the substrate to effect electrical contact between thepressed strip and element without severing the element; and (5) removingthe remaining, unpressed portions of the strip from the substrate.

In accordance with another aspect of the invention there is provided acircuit board assembly which comprises a dielectric substrate, at leastone switching element having a portion thereof pressed within thesubstrate, and a conductive member also pressed within the substrate. Atleast part of the conductive member is positioned atop the pressedportion of the switching element and in electrical contact therewith.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial elevational view, in section, of a photoflash deviceincorporating therein a circuit board assembly in accordance with apreferred embodiment of the invention; and

FIGS. 2-5 represent the steps of producing a circuit board assembly inaccordance with the teachings of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

For a better understanding of the present invention together with otherand further objects, advantages and capabilities thereof, reference ismade to the following disclosure and appended claims in connection withthe above described drawings.

With particular reference to FIG. 1, there is illustrated a partial,elevational view of an electrically-activated photoflash device 20incorporating a circuit board assembly 23 manufactured in accordancewith the unique principles of the instant invention. Device 20, likemany of the photoflash devices described above, includes a plastichousing with rear and forward member 27 and 29, respectively. These twomembers may be secured together, e.g., using cement, or it is alsopossible to produce the entire housing from a single member of suchmaterial. Forward member 29 is light-transmitting to permit lightemitted from each of the several flashlamps 31 (only one shown) to passtherethrough upon lamp ignition. Ignition is achieved when the device'send connector tab or tabs (not shown) are inserted within the socket ofthe camera used therewith and the camera's shutter release buttonactivated. A suitable firing pulse is produced by the camera's powersorce (e.g., piezoelectric element) and passed to the respective lamp 31via the connection provided at the connector tab. This pulse travels upthrough the device's circuitry (runs) 33 which forms part of assembly23. As shown in FIG. 1, the two conductive lead-in wires 35 (only oneshown) of lamp 31 are connected to circuitry 33, said means ofconnection accomplished by such methods as soldering or crimping (e.g.,using metal eyelets). Photoflash devices of this type also typicallyinclude a reflector 37 for promoting forward light output. Reflector 37is preferably of aluminum-coated plastic and located immediately behindlamp 31. Device 10 may further include a sheet of flash-indicatingmaterial 39 (e.g., biaxially oriented polypropylene) which shrinks ormelts when subjected to heat from lamp 31 (through a pair of alignedapertures with reflector 37 and the substrate or board component ofassembly 23) to thereby change the color viewable through the openings41 (one shown) provided in an indicia sheet 43 (also optional). A userof the device is thus provided with a ready means of ascertainingwhether or not a particular lamp or group of lamps has been flashed.Understandably, rear member 27 of the device's housing is alsolight-transmitting to permit viewing in the manner defined. Sheet 43 maybe of paper or thin cardboard.

As stated, photoflash devices containing the above components (excludingof course a circuit board assembly produced in accordance with theteachings of the invention) are known in the art with examples of suchbeing described in detail, for example, in the aforementioned patents.As also stated, it is further known in the art to incorporate radiationsensitive switches as an important element of such devices. Reference isagain directed to assignee's U.S. Pat. No. 4,017,728. These elements,represented generally as numeral 45 in FIG. 1, are also referred to inthe art as radiant-energy-activated switches, quick-disconnect switches,etc., and typically comprise a length (strip) of electricallyconductive, heat shrinkable polymeric material attached to the device'sboard member across a respective aperture 49 (see below). The switchbeing attached at its ends, the midportion thereof is thus spatiallysuspended to avoid physical contact with the heat-absorbing surfaces ofthe circuit board. This arrangement maximizes the speed with whichshrinking and separation of the midportion occurs upon receipt of heatfrom adjacent lamp 31. As shown, lamp 31 and switch 45 are electricallyconnected in series to assure proper connection between theaforementioned power source and remaining, unfired lamps which also formpart of device 20. This mode of operation is fully described in many ofthe aforementioned patents and further detail is not believed necessary.

Switch 45 comprises a thin strip of plastic preferably fabricated from amono- or biaxially oriented polyethylene, polypropylene, polystyrene,polyester, or nylon. The polymeric material itself may be renderedconductive by additives such as carbons or may be made surfaceconductive by deposition of a suitable conductive layer thereon. Theperformance of highly reflective materials, such as aluminizedpolypropylene, can be enhanced by applying a coating or spot (not shown)of dark, light-absorbing material (e.g., ink) on the surface of theswitch which faces lamp 31.

As understood from the foregoing, it is essential that the opposing endsof switch 45 not only be properly secured to the board or substratemember (47) constituting a key element of assembly 23 but also must beelectrically connected to respective, designated portions of circuitruns 33. When using the aforementioned technique of silk-screening, thiselectrical connection was achieved by carrying the circuit pattern overthe ends of the switch's strip. This procedure thus resulted inadditional use of the expensive silver-containing conductive material,yet another disadvantage added to the list cited above. In priordevices, switch 45 was secured to board 47 using an adhesive tape withpressure thereafter applied to hopefully provide securement. Thisprocedure did not prove altogether satisfactory, however, in that thestrip was occasionally removed from the board during subsequentprocesses to which this product was subjected.

In accordance with the teachings of the present invention, switchingelement 45 and the conductive members 33 which form part of the overallcircuitry for the finished circuit board assembly 23 are securedlypositioned on the assembly's dielectric substrate 47 using adie-stamping process. The unique, end result of this process is that theconductive members are secured and electrically connected to theconductive switch element, which is also positively secured, withoutsevering the switching element. With particular reference to FIGS. 2-5,there are shown the various steps of producing assembly 23 in order toachieve this result.

In FIG. 2, switching element 45, preferably comprised of the polyesterMylar having a conductive (aluminum) layer thereon, is positioned abovesubstrate 47 so as to align with an aperture 49 located within thesubstrate. The aluminum conductive layer (not shown) is understandablylocated along the upper surface of the Mylar. Aperture 49 in thefinished product (device 20) permits radiant energy from flashlamp 31 topass therethrough to the aforedescribed indicia sheet 43. Aperture 49also serves to assure that a major portion of element 45 will notphysically contact the upper surface of substrate 47. Such a surface,being heat-absorbing, could serve to reduce the operationaleffectiveness of element 45 during exposure thereof to the intenseenergy from flashlamp 31. Accordingly, element 45 is located onsubstrate 47 so as to bridge aperture 49 (FIG. 2). Initial attachment ofelement 45 is achieved by providing a quantity of adhesion 51 at bothends of the striplike element. Adhesive 51, preferably of thepressure-sensitive variety, may be applied using any of the techniqueswell known in the art. The element 45 and adhesive are located onsubstrate 47 and a suitable pressure (sufficient to activate adhesive 51and form a bond between the substrate and element at these locations) isapplied downwardly on the element's upper surface. A roller or similarmember can be used as the pressure applicator.

The combined substrate and element members are next positioned on a baseor platen 53 which forms part of the larger die-stamping machine. Base53 preferably includes a recessed portion or cavity (not shown) thereinto better accomodate substrate 47, the substrate being positioned withinsaid cavity. A thin strip of conductive material 55 is then orientedabove the substrate 47 in the manner shown in FIG. 3, afterwhich it islowered to substantially cover both substrate and switching element.Material 55 is dead soft aluminum, having a thickness of about 0.002inch. Once in position, the aluminum strip is engaged by two dies 57 and57' which each are secured or form part of an upper platen 59 of themachine. Platen 59 and dies 57 and 57' are preferably both comprised ofsteel (e.g., low carbon). The upper platen is lowered mechanically toeffect said engagement with the positioned strip 55. Downward force isfurther applied by dies 57 and 57' until preselected portions 61 ofstrip 55 and switching element 45 are pressed an established distanceinto substrate 47 (FIG. 4). A total force within the range of about 250to 350 pounds per linear inch of cutting edge (of dies 57, 57') isapplied using the materials and thicknesses described herein. Thedielectric substrate, having a preferred thickness of about 0.043 inch,is embedded a depth of about 0.004 inch at its deepest location(immediately below the outer cutting edges 63 of each die). Asillustrated in FIG. 4, both ends of the striplike switching element 45are thus positively secured within substrate 47 on opposing sides ofaperture 49. Element 45, having an original thickness of about 0.0005inch, possesses a hardness greater than both the dielectric substrate(composed of high impact polystyrene) and aluminum strip and is thus notsubstantially deformed by the die-stamping procedure. This significantfeature is the result of a proper selection of materials and thicknessesfor the components of circuit board assembly. As further understood, thealuminum sheet also possesses a hardness greater than that presented bythe dielectric substrate, at least during the initial stages of thestamping operation. As illustrated in FIG. 5, this selection ofmaterials, thicknesses, and pressures (and, as will be described,temperatures) assures not only retention of the designated portion ofswitching element 45 within substrate 47 but also that the preselected,pressed portion 61 of aluminum strip 55 will also be securedly retainedand at the same time provide positive electrical contact with element45. Contact is formed primarily at two locations, the first being at theextreme, substantially flattened edge 65 of the conductive memberdefined by portion 61, and the second along the common arcuate surface(boundary) 67 between portion 61 and element 45. As shown, theconductive member is also of substantially arcuate configuration withits extreme ends substantially tapered by the die-stamping procedure.This final configuration is due to the increased forces exerted alongthe outer, deeper penetrating parallel edges 63 of the die in comparisonto forces exerted at its more recessed portions. The use of parallelcutting edges 63 understandably permits some parts of strip 55 to remainattached to portion(s) 61 after stamping, if desired. These parts, e.g.,70 in FIG. 1, are also die-stamped within substrate 47 by the apparatusdefined herein and will constitute the remaining section of circuit 33.Parts 70 are not shown in FIGS. 4 and 5 for reasons of clarity.Thicknesses of strip 55 substantially equal to or greater than switch 45were successfully employed. In all instances, the thicknesses of boththe aluminum strip 55 and the switch 45 were substantially less than thedielectric 47. In final, stamped form, conductive member 61 has a widthof (dimension "w") about 0.0625 inch. Only part of member 61 lies atop(or covers) the embedded portion of switch 45, but said part is deemedof sufficient size so as to achieve the purposes intended. Theoverlapping segment of conductive member 61 thus also serves to assistin retention of the embedded portion of switch 45. It is important tonote that while edge 65 does not achieve contact with switch 45, it doesnot deform or sever this element. Severance or even substantialdeformation could render this portion of the circuitry inoperative. Muchof the adhesive (51) which was originally applied to the bottoms of theends of switch 45 pressed within substrate 47 will be forced out fromunder the switch during this operation but some (not shown) will remainto assist in retention. That adhesive material which is forced (orsqueezed) out may settle within the recess 69 located under thenon-covering portion of member 61. Thus, switch 45 provides a relief forthis adhesive in the manner illustrated in FIG. 5.

As also shown in FIG. 3, another adhesive (71) is applied to the bottomof aluminum strip 55. The preferred adhesive is of the heat sensitivevariety (several of which are well known in the art) and preferablypossess a quick reaction time. It can be applied directly to the bottomof strip 55 during manufacture thereof or can be provided in separate,sheet form. The adhesive has a thickness of about 0.0007 inch, and isactivated during the die-stamping process by heating each of the topdies 57 and 57'. Preferred temperatures were within the range of about325 to 400 degrees Farenheit. The bottom or base member 53 was notheated. In the stamping operation, the adhesive 71 engaging the commonsurface 67 will be substantially squeezed out into recess 69, thusassuring the described positive contact along this surface. It wasfound, however, that even if adhesive was to remain at this location,adequate electrical contact was still attained. Subsequent to thisaforedefined stamping procedure, the upper platen 59 is withdrawn (e.g.,to the original elevation shown in FIG. 3) and the remaining,non-stamped part of aluminum strip 55 removed. Removal may beaccomplished by hand or a suitable stripping tool (e.g., roller).

As an optional step, it may be desirable to engage predetermined (e.g.,the uppermost) portions of the defined, stamped conductive member 61with a heated die 77 (shown in phantom in FIG. 5) in the event that theheat sensitive adhesive located immediately under these portions was notfully exposed to the elevated temperatures of dies 57 and 57'. It isunderstood that this is but an optional step and may only be desired forportions of the circuit board assembly's circuitry which will besubjected to great stress (e.g., insertion forces encountered duringpositioning of the finished devices 20 within the socket of a respectivecamera). Die 77 would be heated to a temperature substantially the samefor that of dies 57, 57', should this step be used.

EXAMPLE

Sixty high impact polystyrene substrates, each having a thickness ofabout 0.043 inch, were die-stamped in accordance with the teachingsherein. Each substrate contained a total of eight Mylar switchingelements (having a thickness of 0.0005 inch) spacedly positioned thereonin a desired pattern. A 0.002 inch thick dead soft aluminum sheet wasplaced over each and a heated (350 degrees Farenheit) steel die, havinga dinking depth (depth of cutting edge) of 0.004 inch, was employed. Apressure of 300 pounds per linear foot of cutting edge was applied. Noneof the switching elements were severed by the die's cutting edges or thedead soft aluminum and all possessed a satisfactory electrical contactto the respective, pressed conductive members formed from the aluminum.By way of further example, all of said switches possessed a spark gapcontact (to conductive member) of less than 500 volts. Approximately 99percent of these had a spark gap contact of less than 200 volts. Both ofthese are deemed completely satisfactory for photoflash devices of thevariety utilizing high voltage flashlamps.

Thus there has been shown and described a new and unique circuit boardassembly for use in a photoflash device. In addition, there has beenshown and described a new and unique method for making said assembly. Itis understood from the foregoing description that the invention asdescribed herein possesses all the significant advantages cited above.

While there have been shown and described what are at present consideredthe preferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the scope of the invention as defined bythe appended claims.

What is claimed is:
 1. A method of making a circuit board assembly foruse in a photoflash device wherein said assembly includes a dielectricsubstrate, at least one switching element, and at least one electricalconductive member, said method comprising:positioning said switchingelement at a predetermined location on a first surface of saidsubstrate; positioning said dielectric substrate on a base member;orienting a thin strip of electrically conductive material over saiddielectric substrate and said switching element; engaging said thinstrip of conductive material with a metal die member so as to presspreselected portions of said conductive material and said switchingelement into said dielectric substrate such that said preselectedportions of said conductive material effect electrical contact with saidswitching element without severing said element, said preselectedportions of said conductive material defining said conductive member;and removing the remainder of said electrically conductive material fromsaid substrate member.
 2. The method according to claim 1 furtherincluding providing at least one aperture within said dielectricsubstrate prior to positioning said switching element thereon, saidswitching element thereafter positioned on said substrate so as tosubstantially bridge said aperture.
 3. The method according to claim 2further including applying an adhesive to the portions of said switchingelement which contact said first surface of said dielectric substrateprior to said positioning of said element on said substrate.
 4. Themethod according to claim 3 wherein said positioning of said switchingelement having said adhesive thereon to said substrate is accomplishedby the application of pressure to said switching element.
 5. The methodaccording to claim 1 further including applying an adhesive to saidpreselected portions of said conductive material to be pressed into saidsubstrate member pior to said engaging of said conductive material withsaid die member.
 6. The method according to claim 5 further includingheating said die member to a predetermined temperature prior to saidengaging of said strip of conductive material and thereafter effectingsaid engagement with said heated die member.
 7. The method according toclaim 1 further including engaging a predetermined portion of saidconductive member with a die member subsequent to said removal of saidremainder of said conductive material.
 8. The method according to claim7 further including heating said die member which engages saidpredetermined portions of said conductive member to a preestablishedtemperature prior to said engaging and thereafter effecting saidengagement of said conductive member with said heated die member.
 9. Themethod according to claim 1 wherein said conductive member formed bysaid pressing is of substantially arcuate configuration, the extremeends of said conductive member being substantially tapered, a least oneof said tapered ends providing said electrical contact with saidswitching element.
 10. The method according to claim 9 wherein only partof said conductive member substantially covers the end of said switchingelement pressed within said dielectric substrate, said part assisting inretaining said end of said switching within said substrate.